Very general vintage hone information?
I've accidentally acquired a small collection of vintage hones, all of which I picked up by buying assorted lots of vintage razors. I have a Franz Swaty and a couple Pikes, and many others, and I was recently given a hone that's unmarked. It measures 5.25" x 2.25" and has different-colored sides that meet unevenly and organically around the edges. I was told it's a natural hone, and possibly valuable?
I'm not looking for monetary values. Well actually, I am looking for monetary values, as I'm in the process of selling them, but I understand that sort of thing is against forum policy, and that's not a problem, but I'm trying to learn as much as I can about antique hones so I know what to pay when I find them, and what to sell them for. Looking at sold hones on Ebay isn't much help, especially with the natural ones.
I have yet to find substantial basic information about how to value and appraise hones, and which hones are most desirable among hone collectors, so if anyone can give me some general information, or if you can steer me toward a resource with the info I need, I'd be very appreciative.